Rotors of open end spinning machines are formed with an internal concentric peripheral groove of critical dimensions, there to receive discrete fibers in an overlaying pattern and permit them to twist into a yarn end to then be withdrawn from the rotor as a continuous yarn strand of a desired cross-sectional dimension and uniformity from length portion to length portion therealong.
However, minute particles of foreign matter carried along with the fibers received by the groove in time build up therewithin to change the geometry of the groove in an unequal fashion thereabout to change the characteristics of the yarn formed, and ultimately to produce so weak a yarn that it easily parts, producing what is known as an ends down condition. In common mill practice, it has been found desirable to remove the accretions of foreign matter from the rotor cup grooves in a timely manner prior to a serious deterioration of yarn characteristics. To do this, many techniques have been tried. For example, in some mills after a predetermined running time the spinning operator will move along the row of rotors, stopping each in turn, opening the rotor box, removing the fibers within, digging out the fiber collection groove, closing the box, and restarting the fiber feed and rotor cup rotation, and then feeding back the free end of yarn to make contact with the circlet of fibers for their twisting in, and finally pulling out the newly forming strand of yarn to wind it into a "cheese" in a resumption of production of yarn at that spinning station. Such is manual rotor cleaning and repiecing of the yarn. This process is followed also whenever during production the yarn end "comes down," which is to say that separation occurs between the fiber circlet and the yarn end or between two portions of the yarn between where it leaves the rotor and is wrapped onto the package being formed. If ever the rotor is stopped, such as at the end of some shift perhaps, or if the package is manually doffed perhaps, rotor cleaning and repiecing are pursued, often as a prudent measure to help insure the quality of yarn following these events.
Technologists in the art of rotor cup yarn spinning have solved many of the problems involved in devising apparatus for the mechanical repiecing of yarn and the doffing of cheeses of yarn from and donning tubes onto the machine. However one problem has been unusally resistant to a satisfactory resolution: that of adequate cleaning of rotors' grooves to free them of all foreign matter by mechanical means, and all the while not injuring the groove surfaces or changing their geometries. This problem is better understood with the consideration that the foreign matter particles accreting with processing time, under the heat developed in the rotor and in the presence of resins perhaps on natural fibers and in the form of dressings on synthetic fibers, tenaciously seem to bind themselves both to the metal surfaces of the groove and to one another. In manual cleaning, experienced operators often use wooden "toothpicks" to dig out the accumulations of foreign matter, the wood being soft enough not to injure the metal surfaces of the grooves and being inexpensive enough to use many such wooden "picks" for cleaning at little material cost but at a larger labor cost. They found that yarn produced shortly after cleaning in the foregoing manner was restored to the desired tensile strength and cross-sectional diameter with a strongly improved uniformity in those regards from length portion to length portion therealong. One way to date has been proposed whereby literal "toothpick" cleaning of the collection grooves or rotors may be done mechanically, which is to say by a machine "picking" without human intervention; however even this apparatus falls short of attaining a "toothpick clean" groove. By "toothpick clean" is meant not necessarily that toothpicks must be used, but rather that the degree of cleaning, lack of injury to the surfaces and geometries of the grooves, and the desired restoration of yarn properties be attained in a comparable or better extent as or than can be done by the manual "toothpick" method. Motorized brushes moving even at hundreds of revolutions per minute, motorized plastic scoops with serrated wheel rims have been tried, vacuum nozzles have been employed, and yet, to present knowledge until the advent of the present invention, none have cleaned toothpick clean, producing in essence a bright or burnished clean metal surface at the apex of the collection groove, without damage or change in geometries.